1. Technical Field
This invention relates to the art of accurately setting an arc welding torch in a mechanically fixed orientation to a relatively moving workpiece during welding to enhance the quality of the weld.
2. Discussion of the Prior Art
Arc welding torches can be straight, angled or curved, and the degree of straightness, angle or curvature can vary between manufacturers. Nonetheless, the axis of the gas nozzle for such torches is coincidental with the axis of the welding electrode wire (which is in coincident with the torch contact tip). It is the orientation between (a) the line of movement for weld travel, and (ii) the axis of the electrode wire passing through the weld bead that determines the weld angle. Weld angle is compound, comprising: (a) an inclination between such electrode axis and the line of movement in a plane that is at 90.degree. either to the axis of rotation if the workpiece is rotating relatively or to the first general plane of the workpiece if stationary (often called lead angle), and (b) an inclination between such electrode axis and the line of movement in a plane parallel to the axis of rotation if the workpiece is rotating relatively or to a second general plane at 90.degree. of the first plane if the workpiece is stationary (often called transverse angle).
Torch angle is a critical parameter in welding; in many cases it is second in importance only to welding current. Applicants are unaware of any prior art that is effective in measuring or setting torch angle independent of the workpiece as part of the fixturing. It is common practice to estimate the initial torch angle based upon experience and data, and then modify the angle using protractors by a trial and error technique to arrive at the optimum angle for welding quality in a production run. Attempts to fixture the measurement have consistently resulted in use of devices, often very complex, that contact the workpiece to be welded to establish references (see U.S. Pat. Nos. 3,124,093; 3,443,732; and 4,202,535). This latter approach is disadvantageous because it is cumbersome in automatic robotic applications which are frequently changing and the torch is held independent of the workpiece.
What is needed is a device that not only eliminates estimation, but accurately, quickly, and universally establishes torch angle in three-dimensional space independent of the workpiece, and does so with ease and without complexity.